Linking fish and crustacean taxonomic composition with seasonal contrasts in the soft-bottom intertidal zone

Abstract The primary objective of this study was to investigate the seasonal fish and crustacean variations concerning taxonomic composition, species richness, and diversity in sandy beach habitat. For this purpose, we investigated the Sonmiani Hor lagoon area during four distinct seasons, i.e., northeast (NE) monsoon, pre-monsoon, south-west (SW) monsoon, and post-monsoon for one year. During each haul, the net was pulled about 100m along the beach in 0.5m depth. The results showed a strong linear correlation between the diversity index and equitability in fishes (r = 0.978). The diversity index was strong negatively correlated with the abundance and biomass (r = -0.978, -0.972, respectively). The physical attributes like sea surface water temperature and salinity showed a strong negative effect on species assemblages (r = -0.981 and -0.943, respectively). The mean air and water temperature illustrated approximately 3°C difference during NE and pre-monsoon seasons. However, salinity, pH, and electrical conductivity did not show any significant seasonal variabilities. Under the ecological indices, the fish species displayed higher diversity (H’ = 3.19) during SW monsoon, whereas the lowest diversity was observed during pre-monsoon (H’ = 1.58). The equitability and species richness, however, remained more noticeable during SW monsoon (J’ = 0.81). The total number of individuals of fish and crustaceans reached 4799 with 3813 fish individuals and 986 individuals of crustaceans. A total of 27 families of fish while five crustacean families comprising of 30 genera and 38 fish species while ten genera and 17 species of crustaceans were recorded. Liza subviridis displayed the highest abundance among the sampled fish species. In conclusion, fish species constituted a significant part of the coastal fauna in the study area. The seasonal variations displayed distinct variations in fish species composition and diversity.摘要 本研究旨在探究沙滩生境中鱼类与甲壳类的分类组成、物种丰富度及多样性的季节变化特征。为此，研究团队于一年周期内，针对松米亚尼霍尔（Sonmiani Hor）泻湖区域开展了四个典型季节的采样，分别为东北季风季、季风前季、西南季风季与季风后季。每次采样时，拖网沿沙滩以0.5米水深拖拽约100米。 结果显示，鱼类多样性指数与均匀度呈极强线性相关（r=0.978）；多样性指数与丰度、生物量呈显著负相关，相关系数分别为-0.978与-0.972。海水表面温度、盐度等物理属性对物种群落具有极强负向影响，相关系数分别为-0.981与-0.943。东北季风季与季风前季的平均气温与水温差值约为3℃；而盐度、pH值及电导率未表现出显著季节波动。 在生态指数方面，鱼类群落的多样性在西南季风季达到峰值（H’=3.19），季风前季最低（H’=1.58）；均匀度与物种丰富度则在西南季风季最为突出（J’=0.81）。本次采样共收集到4799个个体，其中鱼类3813尾，甲壳类986只；共记录鱼类27科、30属、38种，甲壳类5科、10属、17种。绿背鮻（Liza subviridis）为采样鱼类中丰度最高的物种。 综上，鱼类是研究区域沿海动物群的重要组成部分，季节变化对鱼类物种组成与多样性具有显著影响。